This invention relates generally to roof membrane seam welders. More particularly, it relates to a seam welder that avoids fastening obstructions and provides a continuous seam weld when obstructions are not present.
When installing a roof, roof membranes are applied over the base structure. Roof membranes, which are made of thermoplastic-based materials such as polyvinyl chloride (PVC), thermoplastic polyolefin (TPO), or thermoplastic poly vulcanites (TPV), repel water, snow, and generally protect the integrity of the underlying structure.
To properly install roof membranes, a fastening device such as a plate, batten bar, or other type of mechanical affixment secures one edge of a membrane to the underlying structure. An edge of a second membrane is then placed over the first membrane and the fastening device. The membranes are then welded to one another by applying a solvent/adhesive and/or by applying heat. The welding process is complicated by the presence of the fastener along the edge of the bottom membrane. As such, it is difficult to obtain a uniform and continuous seam/weld between the adjoining membranes.
One attempt at avoiding obstructions and fasteners is disclosed in U.S. Pat. No. 4,834,828, in which a bifurcated heat element seams the membranes while avoiding the fastening device. Although effective, the disclosed seaming device is deficient inasmuch as some fastening devices do not extend along the entire edge of the membrane and a gap or bubble may form along the welded seam. Accordingly, a secure seal is not obtained by virtue of elements infecting the gap between the seams and allows the membranes to be subjected to uplift pressures and other natural elements. This deteriorates the integrity of the seam which ultimately damages the underlying structure.
A continuous welding machine that can accommodate fastening devices when encountered and provide a continuous weld when obstructions are not present remains an unmet need in the art.
Briefly, the present invention provides an apparatus for seam welding membranes that avoid obstructions when encountered and also provides a continuous width weld when obstructions are not present.
In an apparatus for seam welding membranes that avoids obstructions, there is a wheeled carriage, which may be driven by a motor, that is typically pulled during operation. The apparatus heats both membranes in the area where they are to be seamed to one another. Once a fusing temperature has been reached, a weighted roller assembly applies pressure to the membranes to complete the bonding process.
In order to obtain a continuous seam weld when obstructions are not present and to avoid obstructions when encountered, a specially designed nozzle and roller assembly are used. A heating assembly is mounted on the carriage and exhausts heated air between the two membranes. The heating assembly includes a nozzle which is configured with a plurality of channels, wherein the outer channels are in close association with the bottom and top membranes while the center channel is somewhat elevated above the bottom membrane and in close association with the top membrane. The elevated nature of the central channel allows for the nozzle to avoid any obstructions that are positioned in about the center portion of the seam area. The carriage moves at a relatively low rate of speed so that the heated air can elevate the surface temperature of the membranes to about their melting temperature. Immediately following the nozzle, a roller assembly exerts a uniform pressure upon the two membranes to ensure their bonding to one another. In order to avoid obstructions, the pressure roller assembly incorporates a plurality of rollers. In particular, the roller assembly includes two outer rollers which continually exert a pressure force upon the heated membranes. A center spring-biased pressure roller is disposed between the two outer rollers and, likewise, exerts a uniform pressure upon the membranes in the absence of an obstruction. When an obstruction is encountered, the spring-biased roller assembly is deflected upwardly and then returns after the obstruction has been passed. Accordingly, a substantially continuous width seam is formed between the membranes except where interrupted by a protruding fastener.
The present invention provides an improved method for fusing two membranes to one another while also improving the integrity of the seam therebetween.